perf: remove redundant allocations and copies from the request and response hot paths

impit-node/index.wrapper.js

@@ -23,8 +23,8 @@ Run your script with IMPIT_VERBOSE=1 environment variable to get more informatio
 
 class ResponsePatches {
     static async text() {
-        const buffer = await this.bytes();
-        return this.decodeBuffer(buffer);
+        const buffer = await this.arrayBuffer();
+        return this.decodeBuffer(Buffer.from(buffer));
     }
 }
 
@@ -39,14 +39,18 @@ function canonicalizeHeaders(headers) {
     return [];
 }
 
+const REDIRECT_STATUSES = new Set([301, 302, 303, 307, 308]);
+
 function isRedirectStatus(status) {
-    return [301, 302, 303, 307, 308].includes(status);
+    return REDIRECT_STATUSES.has(status);
 }
 
+const textEncoder = new TextEncoder();
+
 // Stream chunks may be strings (e.g. a ReadableStream or Node stream that wasn't
 // fed bytes); encode them so they aren't coerced to zero bytes by Uint8Array.set.
 function toUint8Array(chunk) {
-    return typeof chunk === 'string' ? new TextEncoder().encode(chunk) : new Uint8Array(chunk);
+    return typeof chunk === 'string' ? textEncoder.encode(chunk) : new Uint8Array(chunk);
 }
 
 // Streamed bodies are passed to the native layer as a ReadableStream of bytes, so that the chunks
@@ -69,7 +73,7 @@ function toByteStream(source) {
 
 function shouldRewriteRedirectToGet(httpStatus, method) {
     // See https://github.com/mozilla-firefox/firefox/blob/911b3eec6c5e58a9a49e23aa105e49aa76e00f9c/netwerk/protocol/http/HttpBaseChannel.cpp#L4801
-    if ([301, 302].includes(httpStatus)) {
+    if (httpStatus === 301 || httpStatus === 302) {
         return method === 'POST';
     }
 
@@ -138,7 +142,6 @@ class Impit extends native.Impit {
 
         const blobParts = [];
         const rn = new Uint8Array([13, 10]);
-        const textEncoder = new TextEncoder();
 
         for (const [name, value] of formData) {
             if (typeof value === 'string') {
@@ -189,9 +192,9 @@ class Impit extends native.Impit {
     // Based on https://github.com/nodejs/undici/blob/14e62db0d0cff4bea27357aa5bd14881459b27c7/lib/web/fetch/body.js#L90
     async #serializeBody(body) {
         if (typeof body === 'string') {
-            return { body: new TextEncoder().encode(body), type: 'text/plain;charset=UTF-8' };
+            return { body: textEncoder.encode(body), type: 'text/plain;charset=UTF-8' };
         } else if (body instanceof URLSearchParams) {
-            return { body: new TextEncoder().encode(body.toString()), type: 'application/x-www-form-urlencoded;charset=UTF-8' };
+            return { body: textEncoder.encode(body.toString()), type: 'application/x-www-form-urlencoded;charset=UTF-8' };
         } else if (body instanceof ArrayBuffer) {
             return { body: new Uint8Array(body.slice()), type: '' };
         } else if (ArrayBuffer.isView(body)) {
@@ -261,9 +264,9 @@ class Impit extends native.Impit {
         signal?.throwIfAborted();
 
         let abortHandler;
-        const waitForAbort = new Promise((_, reject) => {
+        const waitForAbort = signal && new Promise((_, reject) => {
             abortHandler = () => reject(signal.reason);
-            signal?.addEventListener?.("abort", abortHandler, { once: true });
+            signal.addEventListener?.("abort", abortHandler, { once: true });
         });
 
         try {
@@ -296,13 +299,12 @@ class Impit extends native.Impit {
         while (true) {
             signal?.throwIfAborted();
 
-            const headers = [...(options.headers || [])];
-            const hasUserCookie = headers.some(([k]) => k.toLowerCase() === 'cookie');
+            let headers = options.headers || [];
 
-            if (this.#cookieJar && !hasUserCookie) {
+            if (this.#cookieJar && !headers.some(([k]) => k.toLowerCase() === 'cookie')) {
                 const cookieHeader = await this.#getCookies(url);
                 if (cookieHeader) {
-                    headers.push(['Cookie', cookieHeader]);
+                    headers = [...headers, ['Cookie', cookieHeader]];
                 }
             }
 
@@ -314,10 +316,9 @@ class Impit extends native.Impit {
                 bodyStream: method === 'GET' ? undefined : options.bodyStream,
             });
 
-            const originalResponse = await Promise.race([
-                response,
-                waitForAbort
-            ]);
+            const originalResponse = waitForAbort
+                ? await Promise.race([response, waitForAbort])
+                : await response;
 
             const responseHeaders = new Headers(originalResponse.headers);
 
@@ -334,7 +335,7 @@ class Impit extends native.Impit {
                     const location = responseHeaders.get('location');
 
                     if (!location) {
-                        return this.#wrapResponse(originalResponse, signal);
+                        return this.#wrapResponse(originalResponse, signal, responseHeaders);
                     }
 
                     redirectCount++;
@@ -353,17 +354,18 @@ class Impit extends native.Impit {
                 }
             }
 
-            return this.#wrapResponse(originalResponse, signal);
+            return this.#wrapResponse(originalResponse, signal, responseHeaders);
         }
     }
 
     /**
      * Wrap a native response with JS enhancements
      * @param {object} originalResponse
      * @param {AbortSignal} signal
+     * @param {Headers} headers Response headers, already parsed by the caller
      * @returns {object}
      */
-    #wrapResponse(originalResponse, signal) {
+    #wrapResponse(originalResponse, signal, headers) {
         signal?.throwIfAborted();
 
         let abortHandler;
@@ -411,7 +413,7 @@ class Impit extends native.Impit {
         });
 
         Object.defineProperty(originalResponse, 'headers', {
-            value: new Headers(originalResponse.headers)
+            value: headers
         });
 
         Object.defineProperty(originalResponse, 'clone', {

impit-node/src/lib.rs

@@ -120,30 +120,27 @@ impl ImpitWrapper {
     url: String,
     request_init: Option<RequestInit>,
   ) -> Result<ImpitResponse, napi::Error> {
+    let RequestInit {
+      method,
+      headers,
+      body,
+      body_stream,
+      timeout,
+      force_http3,
+      ..
+    } = request_init.unwrap_or_default();
+
     let request_options = Some(RequestOptions {
-      headers: request_init
-        .as_ref()
-        .and_then(|init| init.headers.as_ref())
-        .cloned()
-        .unwrap_or_default(),
-      timeout: request_init
-        .as_ref()
-        .and_then(|init| init.timeout)
-        .map(|timeout| Some(Duration::from_millis(timeout.into()))),
-      http3_prior_knowledge: request_init
-        .as_ref()
-        .and_then(|init| init.force_http3)
-        .unwrap_or_default(),
+      headers: headers.unwrap_or_default(),
+      timeout: timeout.map(|timeout| Some(Duration::from_millis(timeout.into()))),
+      http3_prior_knowledge: force_http3.unwrap_or_default(),
     });
 
-    let method = request_init
-      .as_ref()
-      .and_then(|init| init.method.to_owned())
-      .unwrap_or_default();
-    let body = request_init.and_then(|init| match (init.body, init.body_stream) {
+    let method = method.unwrap_or_default();
+    let body = match (body, body_stream) {
       (_, Some(stream)) => Some(ImpitBody::from_stream(stream.into_byte_stream())),
       (bytes, None) => bytes.map(|array| array.to_vec().into()),
-    });
+    };
 
     let response = if matches!(method, HttpMethod::Get | HttpMethod::Head) && body.is_some() {
       Err(ImpitError::BindingPassthroughError(

impit-node/src/response.rs

@@ -92,7 +92,7 @@ impl<'env> ImpitResponse {
     // JS Fetch semantics: header values are decoded as ISO-8859-1 (each byte 0x00..=0xFF maps to
     // the code point U+0000..=U+00FF). Since that mapping is a bijection, the string stays
     // byte-recoverable via `Buffer.from(value, 'latin1')`.
-    let mut headers_vec: Vec<(String, String)> = Vec::new();
+    let mut headers_vec: Vec<(String, String)> = Vec::with_capacity(response.headers().len());
     for (k, v) in response.headers().iter() {
       headers_vec.push((
         k.as_str().to_string(),

impit-python/src/async_client.rs

@@ -376,13 +376,11 @@ impl AsyncClient {
         url: String,
         content: Option<RequestBody>,
         mut data: Option<RequestBody>,
-        headers: Option<HashMap<String, String>>,
+        mut headers: Option<HashMap<String, String>>,
         timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
         stream: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
-        let mut headers = headers.clone();
-
         if let Some(content) = content {
             data = Some(content);
         }
@@ -392,11 +390,7 @@ impl AsyncClient {
         let timeout = parse_timeout(timeout)?;
 
         let options = RequestOptions {
-            headers: headers
-                .unwrap_or_default()
-                .iter()
-                .map(|(k, v)| (k.clone(), v.clone()))
-                .collect(),
+            headers: headers.unwrap_or_default().into_iter().collect(),
             timeout,
             http3_prior_knowledge: force_http3.unwrap_or(false),
         };

impit-python/src/client.rs

@@ -373,13 +373,11 @@ impl Client {
         url: String,
         content: Option<RequestBody>,
         mut data: Option<RequestBody>,
-        headers: Option<HashMap<String, String>>,
+        mut headers: Option<HashMap<String, String>>,
         timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
         stream: Option<bool>,
     ) -> Result<ImpitPyResponse, ImpitPyError> {
-        let mut headers = headers.clone();
-
         if let Some(content) = content {
             data = Some(content);
         }
@@ -391,11 +389,7 @@ impl Client {
             .map_err(|e| ImpitPyError(ImpitError::BindingPassthroughError(e.to_string())))?;
 
         let options = RequestOptions {
-            headers: headers
-                .unwrap_or_default()
-                .iter()
-                .map(|(k, v)| (k.clone(), v.clone()))
-                .collect(),
+            headers: headers.unwrap_or_default().into_iter().collect(),
             timeout,
             http3_prior_knowledge: force_http3.unwrap_or(false),
         };